The usual leucotomy cut in this country, made through burr holes orientated by means of skull measurements, in the majority of cases enters the brain at about the middle of pars triangularis of the inferior frontal gyrus (Brodmann's Area 45), and if performed in a strictly coronal plane remains entirely within the prefrontal region. Intentionally or unintentionally cuts are not infrequently placed either anterior or posterior to this plane. That cuts made posterior to strictly prefrontal levels are often followed by an unfavourable post-operative course distinguished by particularly severe personality change, persisting incontinence, vasomotor, trophic and neurological disturbances has been demonstrated by Knight (1943), Meyer and Beck (1945), Ziegler and Osgood (1945), Reitman (1946) and others.